The invention relates to an anti-theft device for automobiles, which is an after-loading mechanical anti-theft lock for the automobiles. The invention solves the problems that the existing structure comprising an automobile anti-theft lock hook steering wheel, a brake clutch and a lock catch lever can be damaged easily, and an electronic anti-theft device has the defects of power-off failure and high price. The anti-theft device for the automobiles comprises a bolt lever (1) consisting of a bolt tail (2) and a lock hole (3), and a steering post is locked for steering. The anti-theft device for the automobiles has the advantages of high anti-theft degree, simple and easy manufacture and low cost.